Method of fabricating a heat exchange device



Nov. 28, 1967 T. F. PAULS 3,354,533

METHOD OF FABRICATING A HEAT EXCHANGE DEVICE Filed June 7, 1965 3 Sheets-Sheet 2 in l 11/ [III/l A FIG 4 INVENTOR. THERO/V F PA ULS Wow/ M A 7' TOR/VEV T. F. PAULS 3,354,533

METHOD OF FABRICATING A HEAT EXCHANGE DEVICE 5 Sheets-Sheet 3 Nov. 28, 1967 Filed June 7, 1965 INVENTOR. THERO/V F PAULS B/YF Z A 7' TORNE v as I FIG- 7 United States Patent C) 3,354,533 METHGD 63F FABRHQATENG A HEAT EXCHANGE DEVllE Theron F. Pauls, Godfrey, Ill, assignor to Glin Mathieson tChemical Corporation, a corporation of Virginia Filed June 7, H65, Ser. No. 461,882 3 Claims. (Cl. 29--1S7.3)

This appli ation is a continuation-inpart of my cop ending application Ser. No. 287,240, filed June 12, 1963, now U.S. Patent No. 3,273,227.

This invention relates generally to the fabrication of heat exchange devices, and more particularly to the fabrication of single piece sheet metal heat exchange structures having secondary heat dissipating fins integrated therewith.

A commonly used and eflicient type of heat exchange unit for evaporators, air conditioning, condensers, internal combustion engine cooling radiators, and the like is formed from a plurality of superimposed sheets of metal having internally disposed between the sheets a number of conduits generally in a parallel spaced arrangement extending from a first or intake header to a second or outlet header. One or more of such units may be employed; the conduits or tubes serve to carry a heat exchange medium such as water or other coolant in conductive relationship with another medium such as air or other gas passing between the tubes. This type of construction is typical of automobile radiators where, for example, the heated water issues from the cooling block of the engine with the aid of a pump, first enters one of the two headers, and then passes through a great number of thinwalled, relatively flat, closely spaced tubes between which cooling air is blown and which extend usually vertically from one to the other of the headers. Condensers are also frequently of this same type of construction.

According to one known method of manufacture as illustrated in US. Patent 2,690,002, this type of heat exchange unit may be readily manufactured to provide a great multiplicity of tubes in a sheet of metal. This method involves the application of a suitable predetermined pattern of Weld inhibiting material between component sheets, pressure welding all adjoining areas except those separated by the weld inhibiting material, thereby forming a unified composite panel, and inflating along the unwelded areas to erect the tubes integral with the resultant tubed panel. Full advantage heretofore has not been taken of this method inasmuch as the tubes formed are of rather flat or oval shape with the major dimensions lying within or parallel to the panel in which the tubes are formed. In many applications it is desirable that the tubes extend not only longitudinally but also extend perpendicularly out of the panel to a considerable extent so as to place a greater number of the tubes in spaced parallel relationship rather than a lesser number in the same plane. This design adapts the units to fabrication as single pieces of large size, a lesser number of which may then be put together for installations where the external medium passes through perforations in the panel transversely to it rather than passing parallel to the panel along its surfaces.

In accordance with the concepts of this invention a sheet metal panel is formed according to the procedure of the above mentioned US. Patent No. 2,690,002, to form the desired tubular passageway system in its embryonic form. This panel is then slit along a plurality of parallel spaced apart lines extending between two oppositely disposed headers to define the interconnecting tubes. The areas of the panel lying between adjacent slits are then bent or twisted out of the normal plane of the panel so as to dispose such areas in substantially perpendicular relationship to the plane of the panel.

Patented Nov. 28, 1E6? Secondary heat dissipating fin material is inserted between the parallel opposing surfaces or rolls of adjacent tubes in a novel manner and secured in place, and the tubes fully inflated. This construction, while extremely simple to fabricate and assemble, presents a practical and highly efficient heat exchanger adapted to provide a maximum amount of external heat exchange medium flow between the tubes with a minimum amount of turbulence or impediment thereto.

Having thus generally described my invention it becomes a principal object thereof to provide a method of producing an efficient heat exchange device adapted for transfer of heat between an internal and external heat exchange medium.

Another object of the present invention is to provide a method of producing a heat exchange device having a plurality of parallel heat transfer tubes interconnected between a pair of headers for maximum flow of an internal heat transfer medium.

Still another object of the present invention is to provide a method of producing a heat exchange device being a plurality of heat transfer tubes interconnected between a pair of headers, the tubes being elongate in cross section with the cross sectional major dimension of the tube being disposed at substantially right angles to the normal plane of the panel from which the device is fabricated.

Still another object of the present invention is to provide a method of producing a heat exchange device having a plurality of heat transfer tubes interconnected between a pair of oppositely disposed headers which are bent or twisted out of the normal plane of the panel from which the device is fabricated so as to provide slots or apertures through which an external heat transfer medium may flow unimpeded over the external surfaces of the heat transfer tubes.

It is still a further object of the present invention to provide a method of producing a heat exchange device having a plurality of heat transfer tubes interconnected between a pair of headers and having the major cross sectional dimension disposed at substantially right angles to the normal plane of the panel from which the device is fabricated to provide elongate apertures in which secondary heat dissipating fin stock material is inserted in heat transfer relationship with the outer walls of the tubes to achieve maxmum efliciency of heat exchange between the internal and external heat transfer mediums.

Still another object of the present invention is to pro vide a method of producing a device of the above character in a minimum number of steps of simplified nature.

Further objects and advantages of the present invention will become apparent from the following detailed .escription when considered in conjunction with the ac companying drawings, in which:

FIGURE 1 is a plan view of one embodiment of the completed heat exchange device of this invention;

FIGURE 2 is a composite plan View illustrating a number of steps involved in the fabrication of the device of FIGURE 1;

FIGURE 3 is a sectional view taken on line 33 of FIGURE 2;

FIGURE 4 is a view similar to FIGURE 3 illustrating the device in an intermediate stage of fabrication;

FIGURE 5 is a fragmentary view of the device of FIG URE 1 during an intermediate step in the fabrication of the device;

FIGURE 6 is a fragmentary sectional view similar to FIGURE 5 illustrating a portion of the device of FIG- URE 1, the view being taken on line 6-6 of FIGURE 1; and

FIGURE 7 is a fragmentary sectional view on an enlarged scale taken on line 77 of FIGURE 1.

Referring now to the drawings and particularly to FIG- URE 1, there is seen an illustrative embodiment of this invention which is a heat exchange device generally indicated by the reference numeral 10. The initial stage of fabrication of this device is substantially as set forth in great detail in the above mentioned US. Patent 2,690,002, and is generally illustrated, in conjunction with other steps in the formation of the heat exchange device 10, in FIGURES 2, 3 and 4.

Referring now to FIGURES 2 and 3, it will be seen that the heat exchange device is initially formed from a plurality of superposed flat metal sheets 12 and 14. Sheet 12 has applied thereto a pattern of Weld inhibiting material 16 which is a foreshortened version of the desired pattern of tubular passageways in the finished article. This pattern consists of a pair of parallel bands 18 and 20 which are spaced apart adjacent a pair of opposite edges of the stack of sheets formed by the individual sheets 12 and 14. Interconnecting the two bands 18 and 20 are a plurality of bands 22 of weld inhibiting material which cover the extent of sheet 12 intermediate bands 18 and 20 except for elongated parallel islands 24 which are free of weld inhibiting material, and which also extend between the aforementioned bands 18 and 20. It will become apparent that the bands 18 and 20 of weld inhibiting material correspond to the headers in the finished article and that the bands 22 correspond to the plurality of interconnecting tubes. In order to provide ingress and egress apertures for heat transfer medium, the bands 18 and 20 may be extended to an edge of sheet 12 as indicated at 26. It will also be seen that a marginal portion of sheet 12 along opposite sides transverse to the aforementioned opposite sides has been left free of weld inhibiting material 16 forming a peripheral marginal area 28 with the exception of the two strips 26 extending to one of the transverse edges for the ultimate provision of openings adapted for connection to an external source of heat transfer medium.

The stack of component sheets 12 and 14 with weld inhibiting material 16 sandwiched therebetween is then temporarily secured together as by clamps, spot welding or the like to prevent relative movement between the sheets 12 and 14. The assembly thus formed is then heated to a required temperature and fed through a pair of pressure rolls which exert suflicient pressure on the stack to firmly weld the sheets 12 and 14 together into a single integrated sheet in the areas not coated with the weld inhibiting material 16. Simultaneously with the bonding operation the sheets 12 and 14 undergo a substantial reduction in thickness as well as an elongation in the direction of rolling whereby the foreshortened pattern of weld inhibiting material is stretched to a length corresponding to the desired pattern of tubularpassageways in the finished article. FIGURE 4 illustrates in cross section the unified sheet 30 with the unwelded portions 32 at this stage of the fabrication.

Referring again to FIGURE 2, it will be seen that a plurality of slits 34 are formed in the islands 24 free of weld inhibiting material, the slits extending almost the full length of these islands. Two additional slits 36 are provided in the transverse marginal area free of weld inhibiting material for a purpose hereinafter to become apparent. The slits 34 and 36 may be formed during any desirable stage of the fabrication process, either in the individual sheets 12 and 14, or after the sandwich of sheets 12 and 14 and weld inhibiting material 16 has been formed and temporarily secured together or still alternatively after the aforementioned hot rolling step. Preferably the last mentioned alternative would be selected so as to eliminate both the problem of proper alignment of individual sheets 12 and 14 with slits already formed therein, and the problem of rewelding of adjacent slit edges during the hot rolling step if no weld inhibiting material is inserted between these edges. However, it is apparent that the article is readily adaptable to any of a number of arrangements of the aforementioned 4 steps to achieve the heat exchange device in its embryonic form as illustrated in cross section in FIGURE 4.

As can be seen in FIGURE 5, the areas of the composite sheet 30 between adjacent slits 34 and 36 are then rotated or twisted out of the normal plane of the sheet 30 so as to dispose the major cross sectional dimension of such areas at approximately right angles to the normal plane of sheet 30. The areas 38 between adjacent slits 34 correspond to the tubes 38 before inflation thereof, and the areas between the two outermost slits 34 and the slits 36 correspond to two solid portions 66 and 68, see also FIGURE 1. The rotation of these areas is accomplished by any desirable means, and is of an extent covering substantially all of the length of the slits 34 and 36 previously formed in the unified sheet 30. Of course, when bending the portions of the sheets 30 between the slits, it is desirable to maintain the transition portions 56, which lie between the point of connection between the headers 40 and 42 and the remainder of the tubes 38 which are disposed in the aforementioned perpendicular relationship, as short as possible within the limits of the bending characteristic of the metal in order to provide the maximum length of the resulting apertures 54 for flow of air through the apertures.

The unwelded areas 26 which extend to the transverse edge of the unified sheet 30, see FIGURE 2, may then be mechanically pried open and a suitable nozzle inserted therein and connected to an external source. of fluid pressure. A fluid at a first pressure sufiicient to inflate the tubes and obtain the desired flatness is then pumped into the unwelded portions defined by the weld inhibiting material 16 to partially expand the sheets 12 and 14 over these portions, thereby creating the desired system of internal fluid passageways in partially expanded form. Secondary heat dissipating fins 58, formed for example of closely corrugated or pleated fin stock, is then inserted and positioned within the elongate spaces or apertures 54 between the opposing faces 52 of the partially expanded tubes 38. Since the tubes 38 are only partially expanded, the fins 58 will easily drop into place. Similar fins 62 and 64 may be similarly positioned between the outermost partially expanded passageways and the solid portions 66 and 68, respectively. Thus, additional heat transfer fins are achieved for the outermost passageways.

Subsequently, a fluid at a second pressure suificient to ensure contact between the tube wall and the fin stock is introduced into the same unwelded portions as was the first fluid pressure to completely expand the system of internal fluid passageways to the desired amount. This expansion may be carried out either without external restraint thereby resulting in passageway walls having a substantially rounded configuration, or preferably may be carried out between suitable retaining platens, either flat or shaped, so as to limit the extent to which the passage- 7 way walls can expand outwardly, thus creating a tubular passageway of generally rectangular configuration in cross section, as may be seen in FIGURE 6.

During this additional expansion, the fins 58, 62, and 64 previously inserted between or adjacent the tubes will become secured therebetween in intimate contact with the tubes. At the time the second pressure is applied, or if so desired subsequently, a brazing operation may be performed to assure intimate contact of the fins with the tubes During the brazing operation, the second pressure may be reduced to a level to maintain intimate contact between tube and fin stock. It will be noted from FIGURE 6 that when the tubes 38 are inflated after rotation, the welded portions of sheets 12 and 14 formerly defined by the islands 24 free of weld inhibiting material now constitute oppositely directed flanges 60, thereby leaving the opposing faces 52 of tubes 38 smooth and free of any projecting obstructions. These flanges constitute additional heat transfer stock, and in addition add structural rigidity to the device and reinforce the leading edge of the tubes for minimizing damage thereto. The final position of the fins may be seen in the cross sectional view of FIGURE 7, as at 58.

Referring again to FIGURE 1, it will be seen that upon completion of the above steps the heat exchange device comprises the integrated sheet 30 of generally rectanguar configuration, having the parallel spaced-apart internally disposed headers 4-0 and 42 and the elongate tubular passageway 38. The headers 40 and 42 terminate adjacent an edge of sheet 30 in inlet and outlet openings 44 and 46 respectively, to which conduits 48 and 50 respectively are connected for communication of the heat exchange device with a source of internal heat transfer medium. Furthermore, it will be seen that an external heat transfer medium can flow over the fin stock 58, 62, and 64 secured within the relatively wide and elongate slots or apertures 54, thus materially increasing the available heat exchange area of the device. Communication between the headers 40 and 42 and the interconnecting tubes 38 is maintained through the interior of the tubes 33 which traverses the transition portion 56 of tubes 38.

The advantages of this method include the simplified placement and more secure attachment of the fins within the apertures 54. Furthermore, if so desired, the platens may be provided wi h a shaped surface to form corrugations in the tubes during inflation thereof. Such an expedient would provide more secure contact between the tubes and the fin stock, and additionally would provide to; turbulation of the heat exchange medium within the tu es.

It should be noted that with any of the above embodiments and alternate methods of fabrication, as much cooling capacity as required may be achieved by arranging the heat exchange units in multiples with the headers of the several units being connected in parallel.

It will be apparent from the foregoing description and accompanying drawings that there has been provided a method for producing a heat exchanger which is believed to provide a solution to the foregoing problems and achieve the aforementioned objects. It is to be understood that the invention is not limited to the illustrations described and shown herein which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts, and detail of operation, but rather is intended to encompass all such modifications as are within the spirit and scope of the invention as set forth in the appended claim.

What I claim and desire to secure by Letters Patent is:

1. A method of fabricating a heat exchange device from a composite sheet formed of two superposed planar sheets having a pattern of weld inhibiting material interposed between said sheets, said pattern including a pair of parallel spaced-apart bands located adjacent opposite edges of said composite sheet and extending to a transverse edge of said sheet and a plurality of closely spacedapart bands lying parallel to said transverse edge and joined at opposite ends with said pair of bands, said pair of bands and plurality of bands thereby defining islands free of said weld inhibiting material, said method comprising the steps of (A) slitting said composite sheet in said weld inhibiting material free islands over a major portion of the length thereof to provide a plurality of individual strips of said composite sheet,

(B) bending said strips adjacent the opposite end portions thereof in a rotary direction relative to the longitudinal axis of said strips by approximately 6 to displace the elongate portion of said strips between said end portions out of the normal plane of said composite sheet, thereby forming elongate apertures between adjacent confronting surfaces of said strips,

(C) partially expanding said pattern of weld inhibiting material by applying thereto a fluid at a first pressure to partially expand the areas of said composite sheet covered with said weld inhibiting material,

(D) inserting fin stock into said apertures between said confronting surfaces, and

(E) completely expanding said pattern of weld inhibiting material by applying thereto a fiuid at a second pressure to completely expand the areas of said composite sheet covered with said weld inhibiting material, thereby securing said fin stock in said apertures.

2. A method of producing a heat exchange device from a composite sheet formed of two superposed planar sheets having a pattern of weld inhibiting material interposed between said sheets, said pattern including a pair of parallel spaced-apart first bands located adjacent opposite edges of said composite sheet and extending to a transverse edge of said sheet and a plurality of closely spacedapart second bands lying parallel to said transverse edge and joined at opposite ends with said pair of first bands, said pair of first bands and plurality of second bands thereby defining islands free of said weld inhibiting material, said method comprising the steps of (A) slitting said composite sheet in said weld inhibiting material free islands over a major portion of the length thereof to provide a plurality of individual strips of said composite sheet,

(B) rotating said strips over a major portion of the length thereof by approximately 90 to dispose said strips in a plane substantially perpendicular to the plane of said composite sheet, and

(C) forming a system of partially inflated hollow tubes in said composite sheet corresponding to said pattern of weld inhibiting material by applying thereto a fluid at a first pressure to expand the areas of said composite sheet covered with said weld inhibiting material, said system of partially inflated hollow tubes comprising (1) a pair of first tubes corresponding to said pair of first bands, and

(2) a plurality of second tubes corresponding to said plurality of second bands,

(D) inserting secondary heat exchange fin stock between adjacent confronting surfaces of said second tubes,

(E) inflating said second tubes by applying therein a fluid at a second pressure to expand said second tubes and secure said fin stock between said confronting surfaces, and

(F) brazing said fin stock to said confronting surfaces.

3. The method of claim 2 wherein steps (E) and (F) are performed substantially concurrently.

References Cited UNITED STATES PATENTS 2,999,308 9/1961 Pauls 29l57.3 3,034,204 5/1962 Grenell et al. 29-157.3 3,148,728 9/1964 Grenell et al 29-1573 JOHN F. CAMPBELL, Primary Examiner. P. M. COHEN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No; 3,354,535 November 28, 1967 Theron P. Pauls that error appears in the above numbered pat- It is hereby certified d that the said Letters Patent should read as ent requiring correction an corrected below.

Column 2, line 21, for "exchangendevice being read transfer device hav ng same column 2, line 45, for "maxmum" read maximum Signed and sealed this 31st day of December 1968.

(SEAL) Attest:

EDWARD J BRENNER Commissioner of Patents Edward M. Fletcher, Ir.

Attesting Officer 

1. A METHOD FOR FABRICATING A HEAT EXCHANGE DEVICE FROM A COMPOSITE SHEET FORMED OF TWO SUPERPOSED PLANAR SHEETS HAVING A PATTERN OF WELD INHIBITING MATERIAL INTERPOSED BETWEEN SAID SHEETS, SAID PATTERN INCLUDING A PAIR OF PARALLEL SPACED-APART BANDS LOCATED ADJACENT OPPOSITE EDGES OF SAID COMPOSITE SHEET AND EXTENDING TO A TRANSVERSE EDGE OF SAID SHEET AND A PLURALITY OF CLOSELY SPACEDAPART BANDS LYING PARALLEL TO SAID TRANSVERSE EDGE AND JOINED AT OPPOSITE ENDS WITH SAID PAIR OF BANDS, SAID PAIR OF BANDS AND PLURALITY OF BANDS THEREBY DEFINING ISLANDS FREE OF SAID WELD INHIBITING MATERIALS, SAID METHOD COMPRISING THE STEPS OF (A) SLITTING SAID COMPOSITE SHEET IN SAID WELD INHIBITING MATERIAL FREE ISLANDS OVER A MAJOR PORTION OF THE LENGTH THEREOF TO PROVIDE A PLURALITY OF INDIVIDUAL STRIPS OF SAID COMPOSITE SHEET, (B) BENDING SAID STRIPS ADJACENT THE OPPOSITE END PORTIONS THEREOF IN A ROTARY DIRECTION RELATIVE TO THE LONGITUDINAL AXIS OF SAID STRIPS BY APPROXIMATELY 90* TO DISPLACE THE ELONGATE PORTION OF SAID STRIPS BETWEEN SAID END PORTIONS OUT OF THE NORMAL PLANE OF SAID COMPOSITE SHEET, THEREBY FORMING ELONGATE APERTURES BETWEEN ADJACENT CONFRONTING SURFACES OF SAID STRIPS, (C) PARTIALLY EXPANDING SAID PATTERN OF WELD INHIBITING MATERIAL BY APPLYING THERETO A FLUID AT A FIRST PRESSURE TO PARTIALLY EXPAND THE AREAS OF SAID COMPOSITE SHEET COVERED WITH SAID WELD INHIBITING MATERIAL, (D) INSERTING FIN STOCK INTO SAID APERTURES BETWEEN SAID CONFRONTING SURFACES, AND (E) COMPLETELY EXPANDING SAID PATTERN OF WELD INHIBITING MATERIAL BY APPLYING THERETO A FLUID AT A SECOND PRESSURE TO COMPLETELY EXPAND THE AREAS OF SAID COMPOSITE SHEET COVERED WITH SAID WELD INHIBITING MATERIAL, THEREBY SECURING SAID FIN STOCK IN SAID APERTURES. 